Another hurricane—Maria—is barrelling across the islands of the Caribbean, and scientists with the National Hurricane Center are warning that it could hit Puerto Rico and the Virgin Islands as a "potentially catastrophic" storm. In less than a day, the hurricane blew up from Category 1 to Category 5 with 160 mph winds that tore away roofs as it struck the tiny island nation of Dominica.
Forecasters are able to predict hurricane behavior fairly accurately a few days out now. But to determine more precisely and earlier how hurricanes like this will strengthen and move, they need a better understanding of how oceans are warming, how land temperatures and vegetation are changing, and the impact these changing climates will have on the storms themselves.
That knowledge can be a matter of life and death for people in the path of storms as communities and relief agencies prepare for storm impacts and recovery efforts.
Ocean Heat Influences Hurricane Behavior
Understanding how much heat has been trapped deep in the ocean by greenhouse gases is one critical piece of more accurate forecasts, said Kevin Trenberth, an atmospheric scientist with the National Center for Atmospheric Research.
Hurricanes, he explained, interact strongly with the ocean. They churn up the upper ocean and tap into its heat, offloading it into the winds and rain through evaporation. That fuels storms even as they serve as a "relief valve" for the ocean. Global warming, as it heats the ocean, is a source of fuel for more intense storms.
"So, a hurricane is really a climate phenomenon, and, increasingly, the better forecasts have to include a good ocean model underneath," Trenberth said.
The top European weather computers are often more accurate at forecasting hurricane tracks and behavior because they are better at combining and processing information from the atmosphere and real-time ocean data, he said. U.S. experts are working on improvements, but they "can and should do better."
Global warming is changing the very structure of the ocean, including the way different temperature layers mix. That mixing is also important to the evolution of hurricanes, said Penn State climate researcher Michael Mann. A better understanding of the feedback from warming oceans will help resolve the vexing challenges of precisely predicting hurricane tracks and intensification, he said.
Climate Change on Land also Affects Storms
Trenberth said the question of how hurricanes interact with land illustrates another reason you can't separate climate science from hurricane forecasting.
The brushing of Cuba by Hurricane Irma in early September slowed the hurricane down and took some oomph out of it, but the models don't incorporate that interaction with land as well as they could, he said.
"So, once again, the interactions of the hurricane with land and vegetation is a climate problem. But the U.S. Congress is cutting climate research and ocean observations, even as the need grows," Trenberth said.
Trump's Budget Cuts Could Slow This Research
Trump administration officials have refused to discuss links between climate change and hurricanes, triggering a political debate in the midst of multiple climate catastrophes.
The president's proposed budget would cut satellite program funding by 17 percent and curtail international collaboration by U.S. science agencies, and his nominated NASA chief has previously sought to shift NASA funding away from monitoring Earth.
That could hamper efforts to make better forecasts for hurricanes and other extreme climate events and also interferes with efforts to communicate that information to the public, said UCLA atmospheric scientist Daniel Swain.
"What we want people to understand is that climate changes the envelope of weather," Swain said. "Global warming is driving climate extremes beyond those boundaries."
"The events that were once thought to have been vanishingly rare, are not so rare anymore," he said. "This is a problem in a society where we build our infrastructure to last many decades, on the assumption that our climate does not change over 50 years."